This application claims priority under 35 U.S.C. xc2xa7119 from Malaysian patent application serial number PI 20005886, filed Dec. 14, 2000.
This invention relates to a process for the recovery of minor components and refining of vegetable oils and fats from crude vegetable oils and fats, in particular, a process for the recovery of minor components and refining of vegetable oils and fats from seed oil, pulp oil and other vegetable matter.
Crude palm oil contains less than 5% of free fatty acid (FFA). The main fatty acids are palmitic acid and oleic acid. During fractionation, fatty acid is slightly concentrated in the palm olein. Crude palm oil contains 600-1000 ppm of tocotrienol/tocopherol mixture. The tocotrienol presence in palm oil are xcex3-tocotrienol, xcex1-tocopherol, xcex1-tocotrienol and xcex4-tocotrienol in an approximate ratio of 5:2:2:1. Tocotrienol is also enriched in the palm olein during fractionation. Tocotrienol was claimed to be very effective in cholesterol lowering, preventing arteriosclerosis and stroke, inhibits breast cancer cells, protecting the skin against the effects of ultraviolet radiation and as powerful antioxidant.
Typical crude palm oil contains more than 4% of diglyceride. Diglyceride is considered undesirable as it affects crystallization during fractionation. Based on long term human study on feeding of diglycerides-rich cooking oil, diglyceride was said to be able to reduce serum triglycerides, increased serum high density lipoprotein (HDL)-cholesterol and reduction in plasminogen activator inhibitor.
Crude palm oil contains about 500-700 ppm of carotene. The main carotene components are xcex2-carotene and xcex1-carotene. During fractionation, carotene is concentrated in the olein (liquid) fraction. Crude palm olein can contain up to 1500 ppm of carotene whereas crude palm stearin (the solid fraction) has much lower carotene (as low as less than 200 ppm). Consumption of a mixture of natural carotene was claimed to provide protection towards free radical mediated degenerative diseases such as cancer and cardiovascular diseases. It was also claimed that xcex1-carotene but not xcex2-carotene inhibited liver carcinogenesis. It was also claimed that intake of palm carotene inhibits skin peroxidation induced by ultraviolet radiation.
There are patents describing the production of refined red palm oil from crude palm oil. These include U.S. Pat. No. 5,932,261 and Australian Patent Application No. P18770/88. All these patents involved molecular distillation of palm oil at relatively high temperature to remove the fatty acid.
There are also patents describing the production of carotene concentrate from crude palm oil. These include U.S. Pat. Nos. 5,157,132, 6,072,092, 5,019,668 and U.K Patent No. GB2160874A, GB2218989A and GB1515238. Again all these patents involved pretreatment to the free fatty acid, molecular distillation and followed by the process of post treatment such as using adsorbents.
This invention relates to the process of producing refined red oils and fats, carotene concentrate, distilled fatty acid, tocotrienol and sterol concentrate, and diglyceride from carotene-containing natural oils and fats and has particular but not exclusive application to the process of producing these products from crude palm oil and its fractionated products by first removing the polar components prior to transesterification and therefore no post-treatment is necessary after distillation.
This invention has many advantages. It can refine palm oil and palm oil fractionated products without destroying the carotene at a lower vacuum distillation temperature since the polar components including that of odoriferous materials and free fatty acid are removed by alcohol extraction prior to distillation. It also can refine crude palm oil or its fractions into the refined, bleached and deodorized (R.B.D) oils without using degumming agent such as phosphoric acid and deodorized at a significantly lower temperature as most of the free fatty acid and odoriferous materials have been removed.
This invention also enables transesterification to be carried out without pre-esterification of free fatty acid. It also enables production of carotene concentrate without the need of post-distillation treatment such as using adsorbent. As the polar components had been removed from the oil prior to transesterification, the transesterification reaction was carried out without interference from the unsaponifiable matter and carotene remained in the residue. The processes described in the present invention are simpler and cost-effective as compared to that described in other patents on carotene recovery from palm oil. This invention also enables the recovery of FFA, tocotrienol, tocopherol, sterol and diglyceride and other useful minor components of palm oil.
The object of the present invention is to provide a process for the recovery of minor components and refining of vegetable oils and fats from crude vegetable oils and fats without destroying naturally occurring components in the crude vegetable oils and fats.
Accordingly, there is provided a process for the recovery of minor components and refining of vegetable oils and fats wherein said process is:
A process for the recovery of minor components and refining of vegetable oils and fats without destroying naturally occurring components, said process comprising the steps of:
a) removal of polar components from the crude vegetable oils and fats using lower alkyl alcohol or any lower alkyl alcohol-water mixture;
b) removal of alcohol from the product obtained in step (a) by distillation;
c) addition of suitable quantity of bleaching earth to the product obtained in step (b) at normal bleaching temperature followed by filtration; and
d) deodourization of the product obtained in step (c) at a low temperature.
This invention will be clearly understood and apparent with reference to the detailed description which follows.
The features and details of the invention, either as steps of the invention or as combinations of parts of the invention will now be described. It will be understood that the particular embodiments of the invention are shown by way of illustration and not as limitations of the invention. The principle features of the invention may be employed in various embodiments without departing from the scope of the invention.
Carotene is non-polar in nature. It is freely soluble in oils and fats. Its solubility in lower alkyl alcohol is low. Natural oils and fats consist mainly of triglyceride, which also has low solubility in lower alkyl alcohol such as methanol and ethanol. Oils and fats are soluble in n-propanol, isopropanol and other lower alkyl alcohol. Addition of water or a mixture of these lower alcohol water mixtures can be used to form two phases in the presence of oils and fats.
By using polar solvent such as lower alkyl alcohol or lower alkyl alcohol-water mixture, the polar components such as FFA, tocopherol, tocotrienol, sterol, triterpene alcohol, mono-glyceride, di-glyceride, glycolipid and phospholipid can be extracted out from oils and fats, remaining the non-polar components such as carotene, squalene and triglyceride.
The oil or fat after lower alkyl alcohol extraction can be subjected to washing with water. Residual solvent and/or water can be vacuum distilled at a temperature less than 100xc2x0 C. without destroying tocopherol and tocotrienol in the methanol extract. The mixture of FFA, tocopherol, tocotrienol, sterol, triterpene alcohol, mono-glyceride and di-glyceride can be used for their recovery.
A 1-liter crude palm olein of sample was vigorously stirred with methanol at oil to methanol ratios of 1:1, 1:2, 1:3 and 1:4. Table 1 summarizes the results
The solvent extraction can be carried out at room temperature (about 32xc2x0 C.). It was observed that carotene content increases after removal of the polar materials. It is understood that other room temperatures can also be used. There is no advantage to carry out the extraction at the methanol refluxing temperature or other temperature between room temperature and methanol refluxing temperature. At methanol refluxing temperature, more neutral oil (triglyceride) was extracted and the carotene content is lower than that of the starting material indicating some deterioration of carotene under those conditions. Table 2 summarizes the methanol extraction that was carried out at the methanol refluxing temperature.
It is understood that other polar solvents such as other lower alkyl alcohols or their water mixture can also be used as solvent to extract components such as free fatty acid, tocopherol, tocotrienol, sterol, triterpene alcohol, mono-glyceride and di-glyceride) from natural oils and fats.
For lower alkyl alcohol with three or more carbons, such as iso-propanol and n-propanol, addition of water is necessary to form two phases with the oil. Table 3 revealed the effect of water content in isopropanol after the first extraction at room temperature, using the oil to solvent ratio of 1:2. The addition of water at 5% volume to isopropanol is preferred over the higher water content.
The carotene-containing oil after the methanol extraction still contains about 10% methanol. The methanol can be removed by vacuum distillation at a temperature not more than the 65xc2x0 C. (boiling point of methanol) and the product is refined red palm oil or refined red palm oil fractions such as refined red palm superolein, refined red palm olein and refined red palm stearin. It is understood that anti-oxidants, either natural or synthetic in origin or a combination of both can be added to the red palm oil or its corresponding fractionated products. It is also understood that anti-oxidants, either natural or synthetic in origin or a combination of both can be added to the carotene containing oil before distillation of methanol.
The subsequent carotene-containing oil can be used directly for esterification. In a preferred embodiment, transesterification with 6 molar volume of methanol in the presence of 0.5% sodium hydroxide as catalyst is used. It is understood that acid-catalyzed esterification or transesterification with other bases such as sodium methoxide or potassium hydroxide or at other suitable amounts of methanol and/or catalyst can also be used. It is also understood that small amount of vegetable oil such as sunflower oil can be added into the carotene-containing oil prior to distillation or in the residue receiving vessels for collecting the carotene concentrate.
Transesterification process is monitored by high-resolution gas liquid chromatography using Restek Rtx 65TG column with hydrogen as carrier gas. Glycerol-rich layer can be phased separated and drained continuously or when the reaction is toward completion. The reaction is complete when all the triglyceride and diglyceride peaks disappear in the chromatogram.
The methyl ester layer is centrifuged, with or without addition of small quantity of water to remove small quantity of soap and methanol.
The methyl ester layer is then vacuum distilled. In a preferred embodiment, the methyl ester is degassed in a thin film evaporator, and vacuum distilled less than 3 Pa and at less than 160xc2x0 C. in two stages of short path evaporator. It is understood that degassing can also be carried with short path evaporator or other suitable vacuum distillation unit. It is also understood that distillation of methyl ester can be carried out with different number of evaporator stages. Carotene concentrate is collected as residue.
Methanol in the glycerol layer is distilled at less than 100xc2x0 C., preferably under vacuum of less than 20,000 Pa. Glycerol is distilled at less than 160xc2x0 C. under vacuum of 100 Pa. The methanol extract is distilled to remove the methanol. The residual methanol extract is then subjected to degassing and vacuum distillation in short path evaporators. FFA are distilled first, followed by tocotrienols, tocopherol and sterols, and finally diglycerides. In a preferred embodiment, FFA are distilled at about 200xc2x0 C. under vacuum of 2 Pa, tocotrienol, tocopherol and sterol at less than 220xc2x0 C. under vacuum of 0.1 Pa, and diglyceride at 271xc2x0 C. under vacuum of 0.1 Pa.
After methanol removal, the oil after methanol extraction can be processed into R.B.D. oil by treatment with 0.5% of bleaching earth at 90 to 120xc2x0 C. under partial vacuum, filter and deodorized at 170 to 240xc2x0 C. under vacuum of 300 to 500 Pa. It is understood that higher dosage of bleaching earth and/or higher deodorization temperature can also be carried out. The oil refined using this process do not need degumming with phosphoric acid, uses less bleaching earth and deodorized at lower temperature as the process had already removed the fatty acid and odoriferous materials prior to refining.
After methanol removal, the oil after methanol extraction can be fractionated or further fractionated. Since most of the diglycerides and unsaponifiable matter have been removed prior to the fractionation process, the crystallization behavior is more predictable as compared to the conventional fractionation of palm oil.
The present invention will now be further specifically described by the following examples. All parts and percentages are by weight unless otherwise stated.